Angular rate sensor

ABSTRACT

An object of the present invention is to improve the efficiency of a driving operation of an angular rate sensor employing a tuning fork oscillator made of single crystalline piezoelectric material such as quartz. In order to achieve the object of the present invention, a tuning fork oscillator assembled directly has driver electrodes and detector electrodes provided on a first main surface, a second main surface, an outer surface, and an inner surface of a arm, respectively. The oscillator also has a driver electrode, a monitor electrode, and detector electrodes provided on a first main surface, a second main surface, an inner surface, and an outer surface of the other arm thereof, respectively. A driving voltage is supplied from a driving power source so that the two driver electrodes may be equal in the polarity while the polarity of the driver electrode is opposite to that of the driver electrodes.

TECHNICAL FIELD

The present invention relates to an angular rate sensor for an attitudecontrolling and navigation of mobile units including air crafts,automobiles, robots, vessels, and vehicles, for a protection from wobbleof a still camera or video camera hands, and for a remote controller forremote controlling.

BACKGROUND ART

A monolithic type of an angular rate sensor is known as fabricated bydirectly bonding two quartz counterparts as single crystallinepiezoelectric materials in the direction of the crystallographic axisand the thickness which create opposite polarities of piezoelectriceffect and then cutting them into a tuning-fork shape. FIG. 15 is aschematic view of the arrangement of electrodes on arms of a tuning forkoscillator in the angular rate sensor. The sensor will be describedbelow.

As shown in FIG. 15, the tuning fork oscillator 100 has arms 100 a and100 b. The tuning fork oscillator 100 also has a set of electrodes 101to 108 provided on the arms 100 a and 100 b substantially throughout thewhole length. Each electrode is formed by sputtering or vapor depositinga layer of Cr on a base material and then sputtering or vapor depositinga layer of Au, Ag, Al, or the like on the Cr layer. A pair of driverelectrodes 101 and 102 are mounted on a first main surface and a secondmain surface of the arm 100 a, respectively. A monitor electrode 106 ismounted on the second main surface of the arm 100 a. Groundingelectrodes 103, 104, and 105 are mounted on outer and inner surfaces ofthe arm 100 a and a first main surface of the arm 100 b, respectively. Apair of detector electrodes 107 and 108 are mounted on inner and outersurfaces of the arm 100 b, respectively.

For a piezoelectric oscillation along the main surfaces of the tuningfork oscillator 100 at a resonance frequency, the pair of the driverelectrodes 101 and 102 mounted on the arm 100 a are connected to anoscillator 109 and electrically driven by the oscillator 109. Theamplitude of the oscillation on the tuning fork oscillator 100 developedby the oscillator circuit 109 is measured by the monitor electrode 106mounted on the second main surface of the arm 100 b. An angular rateinput about the axis of the tuning fork oscillator 100 generates aCoriolis force in a direction vertical to the main surface of the arm100 b. The force develops a stress on the arm 100 b, and then the stressis detected by the detector electrodes 107 and 108 piezoelectrically.

A charge generated on the monitor electrode 106 is amplified by anexternal circuit and transferred to an automatic gain control (AGC)circuit. Then, it is compared with a reference level signalpredetermined by the AGC circuit. The circuit controls the oscillator109 in order to maintain a constant amplitude of the oscillation of thetuning fork oscillator 100. A signal from the detector electrodes 107and 108 is amplified by an external circuit. The signal issynchronously-detected with the oscillation of the tuning fork detectedby the monitor electrode 106, so that a signal with the Coriolis forcemodulated by the tuning fork oscillator 100 may be demodulated. Then,the signal has an undesired frequency component cut off by a low passfilter (LPF), and is output as a sensor output.

The conventional angular rate sensor having the foregoing arrangementhas the paired driver electrodes provided on the main surfaces of one ofthe arms. Thus, this makes the driving operation of the tuning forkoscillator electrically driven with a constant voltage be hardlyimproved.

SUMMARY OF THE INVENTION

The present invention is developed for solving the above drawback andthe object is to provide an angular rate sensor which is improved in theefficiency of the driving operation.

In order to achieve the object of the present invention, an angular ratesensor includes a tuning fork oscillator having a first oscillatormember of a single crystalline piezoelectric material composed of atleast two arms and a base joining the two arms and a second oscillatormember of the single crystalline piezoelectric material having asubstantially identical shape to the first oscillator member. The twooscillator members are bonded directly to each other in the direction ofthe crystallographic axis and the thickness so that opposite polaritiesof a piezoelectric effect may be developed along the widthwise directionof the oscillator members. The tuning fork oscillator thus includes atleast two arms and a base. The sensor further includes: first, second,third, and fourth electrodes provided on a first main surface, a secondmain surface, an outer surface, and an inner surface of one of the twoarms of the tuning fork oscillator, respectively; a fifth electrodeprovided on either a first main surface or a second main surface of theother arm of the tuning fork oscillator; and sixth and seventhelectrodes provided on an inner surface and an outer surface of theother arm of the tuning fork oscillator, respectively.

When the fifth electrode is provided on the first main surface, adriving voltage is applied to the second and fifth electrodes at thesame polarity, and applied to the first electrode at the reversepolarity against the second and fifth electrodes.

When the fifth electrode is provided on the second main surface, adriving voltage is applied to the second and fifth electrodes at theopposite polarity to each other, and applied to the first electrode atthe same polarity as the fifth electrode.

The angular rate sensor has the efficiency of a driving operationimproved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a tuning fork oscillator, seen from afirst main surface of an angular rate sensor according to Embodiment 1of the present invention.

FIG. 2 is a perspective view of the tuning fork oscillator seen from asecond main surface.

FIG. 3 is a schematic view illustrating the positional arrangement ofelectrodes on arms of the angular rate sensor.

FIG. 4 is a block diagram of an electric circuit of the angular ratesensor.

FIG. 5 is a schematic view of the positional arrangement of electrodeson arms in an angular rate sensor according to Embodiment 2 of thepresent invention.

FIG. 6 is a schematic view of the positional arrangement of electrodeson arms in an angular rate sensor according to Embodiment 3 of thepresent invention.

FIG. 7 is a schematic view of the positional arrangement of electrodeson arms in an angular rate sensor according to Embodiment 4 of thepresent invention.

FIG. 8 is a schematic view of the positional arrangement of electrodeson arms in an angular rate sensor according to Embodiment 5 of thepresent invention.

FIG. 9 is a schematic view of the positional arrangement of electrodeson arms in an angular rate sensor according to Embodiment 6 of thepresent invention.

FIG. 10 is a schematic view of the positional arrangement of electrodeson arms in an angular rate sensor according to Embodiment 7 of thepresent invention.

FIG. 11 is a perspective view of a tuning fork oscillator, seen from itsfirst main surface of an angular rate sensor according to Embodiment 8of the present invention.

FIG. 12 is a perspective view of the tuning fork oscillator seen from asecond main surface.

FIG. 13 is a perspective view of a modification of the same seen from afirst main surface.

FIG. 14 is a perspective view of a modification of the same seen from asecond main surface.

FIG. 15 is a schematic view illustrating the positional arrangement ofelectrodes on arms in a conventional angular rate sensor.

BEST MODES FOR EMBODYING THE INVENTION Embodiment 1

FIG. 1 is a perspective view of a tuning fork oscillator, seen from thefirst main surface of an angular rate sensor according to Embodiment 1of the present invention. FIG. 2 is a perspective view of the tuningfork oscillator seen from a second main surface. FIG. 3 is a schematicview illustrating the positional arrangement of electrodes on arms inthe angular rate sensor. FIG. 4 is a block diagram of an electriccircuit of the angular rate sensor. As shown in FIGS. 1 and 2, referencenumerals 20 a and 20 b denote arms, which are oscillating portions,joined to each other at a base 20 c, a fixing portion, thus forming anoscillator member 20. Similarly, reference numerals 30 a and 30 b denotearms, oscillating portions, joined to each at a base 30 c, a fixingportion, thus forming an oscillator member 30. The oscillator members 20and 30 are made of single crystalline piezoelectric material and bondeddirectly to each other to have a bimorph structure thus forming a tuningfork oscillator 10. The tuning fork oscillator 10 thus includes arms 10a and 10 b and a base 10 c. For the direct bonding, elements to bebonded have the surfaces smoothed, hydrophilized, absorbed withhydrides, joined to each other, and heated up for removing the hydridesand hydrogen from the interface. As a result, the elements are bondedlike a single structure.

The oscillator member 20 has a crystallographic axis in the leftwarddirection on the figure. The oscillator member 30 has a crystallographicaxis in the rightward direction on the figure. The oscillator members 20and 30 are bonded to each other so that the crystallographic axes (alongthe x-axis) for generating piezoelectric forces extend in oppositedirections against each other.

On the tuning fork oscillator 10, reference numerals 1 through 8 denoteelectrodes. Denoted by numerals 1, 2, and 5 are driver electrodesmounted on the first and second main surfaces of the arm 10 a and thefirst main surfaces of the arm 10 b, respectively. The driver electrodes1, 2, and 5 extend almost throughout the whole length of the arms 10 aand 10 b. They are provided by sputtering or vapor depositing a layer ofCr on a base material and then sputtering or vapor depositing a layer ofAu, Ag, or Al on the layer of Cr. Electrode pads and lead-out portionsof the electrodes are provided on the base 10 c of the tuning forkoscillator 10. The lead-out portions of the electrodes on the base 10 cof the tuning fork oscillator 10 is finer than the electrodes on thearms 10 a and 10 b of the tuning fork oscillator 10, thus they cansignificantly be spaced from each other. This allows the couplingcapacitance between the electrodes to be minimized.

In Embodiment 1, reference numeral 6 denotes a monitor electrode 6 onthe second main surface of the arm 10 b. And reference numerals 3 and 8denote detector electrodes on outer surfaces of the arms 10 a and 10 b,respectively, which are connected to each other. Reference numerals 4and 7 denote detector electrodes on inner surfaces of the arms 10 a and10 b, respectively, which are connected to each other. The detectorelectrodes 4, 7 are linked to the electrode pad 15 through a lead-outportion 15 a patterned on the first main surface of the base 10 c. Thedetector electrodes 3, 8 are linked to the electrode pad 16 through alead-out portion 16 a patterned on the first main surface of the base 10c. The driver electrodes 1, 2, and 5 are linked to electrode pads 11,12, and 13 and lead-out portions 11 a, 12 a, and 13 a, respectively,patterned on the first main surface of the base 10 c. The electrode pad14 and lead-out portion 14 a of the monitor electrode 6 are patterned onthe first main surface of the base 10 c. The lead-out portions 13 a, 14a, and 16 a extend from the driver electrode 2 on the second mainsurface to the electrode pad 13, from the monitor electrode 6 on thesecond main surface to the electrode pad 14, and from the detectorelectrodes 3 and 8 on the outer surfaces to the electrode pad 16,respectively. The lead-out portions are patterned on the second mainsurface and the outer surfaces of the base 10 c then reach the firstmain surface. The positional arrangement of the electrodes in Embodiment1 is illustrated in FIG. 3.

An operation of the angular rate sensor of Embodiment 1 will bedescribed. Between the driver electrode 1 and the driver electrodes 2,5, two alternating currents having a phase difference of 180 degreesfrom each other are supplied by a drive source 9. The arms 10 a and 10 boscillate in leftward and rightward directions (along the main surfaces)in FIG. 3, respectively. In FIG. 3, the arrows denoted by solid linerepresent the crystallographic axis of quartz (electric axis). Thearrows denoted the one-dot chain line represent the direction of anelectric field.

Between the driver electrodes 1, 2, and 5, the alternating currentsignal is supplied from the drive source 9. The driver electrode 1 isloaded with a positive electric field, and the electrodes 2, 5 areloaded with a negative electric field at a certain time. Accordingly, inthe left half from the widthwise center of the arm 10 a, the electricfield is applied in the same direction as the electric axis orpolarizing direction, and thus, the left half of the arm 10 a isexpanded. On the other hand, in the right half of the arm 10 a, theelectric field is applied in a direction opposite to the electric axisor polarizing direction, hence being contracted. As a result, the arm 10a bows toward the inside (the right side) in FIG. 3. Then, when thealternating current from the drive source 9 has the polarity inverted,the arm 10 a bows toward the outside (the left side) in FIG. 3.Repeating the operation makes the arm 10 a perform a resonantoscillation.

In the left half from the widthwise center of the arm 10 b, oppositelyto the arm 10 a, the electric field is applied in a direction oppositeto the electric axis or polarizing direction, and thus, the left half ofthe arm 10 b is compressed. In the right half of the arm 10 b, theelectric field is applied in the same direction as the electric axis orpolarizing direction, thus being expanded. As a result, the arm 10 b isbows toward the inside (the left side) in FIG. 3. Then, when thealternating current from the drive source 9 is inverted, the arm 10 bbows toward the outside (the right side) in FIG. 3. Repeating theoperation makes the arm 10 b perform a resonant oscillation.

During the resonant oscillation, when an angular rate Ω is applied aboutthe Y axis, the arms 10 a and 10 b develop a force along the Z-axisvertical to the oscillating direction along the X axis due to a Corioliseffect and thus deflects in a direction of thickness. According to thedegree of deflection, a charge is sensed signal by the detectorelectrodes 3, 4, 7, and 8 as an angular rate. The charge is then outputfrom common ports S+, S−. To explain it in more detail, for example, anangular rate produces a Coriolis effect which deflects the arm 10 atoward the upper side of FIG. 3 and the arm 10 b toward the lower side.As the lower half of the arm 10 a is expanded, a charge is generated inthe same direction as of the electric axis or polarizing direction. Onthe other hand, as the upper half of the arm 10 a is compressed, acharge is generated in a direction opposite to the electric axis orpolarizing direction. At this moment, oppositely to the arm 10 a, thelower half of the arm 10 b is compressed, and a charge is generated in adirection opposite to the electric axis or polarizing direction, and theupper half of the arm 10 b is expanded, and a charge is generated in thesame direction as the electric axis or polorizing direction. As aresult, in the common port S+, a positive charge is generated, and inthe common port S−, a negative charge is generated. The angular rate isdetected from the charges. Then, the Coriolis effect deflects the arm 10a toward the lower side and the arm 10 b toward the upper side in FIG.3. As the polarity of each charge generated on the arms is inverted,i.e., a negative charge is generated the common port S+, and a positivecharge is generated in the other common port S−, the angular rate isdetected from the charges.

FIG. 4 is a block diagram showing an electric circuit of the angularsensor. A driver circuit will be explained at first. A driver circuitincludes a current amplifier 40, a comparator 41, an AGC circuit 42, andan inverter 43 assembled to form a self-excited oscillator. The monitorelectrode 6 of the tuning fork oscillator 10 develops a chargecorresponding to the amplitude of an oscillation. The charge is receivedby the current amplifier circuit 40 and compared by the comparatorcircuit 41 with a predetermined reference level for maintaining aconstant amplitude. For example, when the amplitude of the charge isgreater than the reference level, the AGC circuit 42 applies anappropriate level of sine-wave signal to the driver electrodes 2, 5 viathe driver electrode 1 and the inverter 43 for attenuating theamplitude. When the charge is smaller than the reference level, the AGCcircuit 42 applies a sine-wave signal to the driver electrodes 2, 5 viathe driver electrode 1 and the inverter circuit 43, so that theamplitude may increases to a desired level. By repeating this action, aconstant amplitude of the output of the tuning fork oscillator 10 can bemaintained.

In a detector circuit, the charges having different polarities and beingin proportion with the angular rate is generated by the Coriolis effecton the detector electrodes 3, 4, 7, and 8. The charges are received by adifferential amplifier 44, phase-advanced in 90 degrees by a phaseshifter 45, and synchronously-detected by a synchronous detector 46 towhich an output of the current amplifier 40 in the driver circuit issupplied. As a result, only an angular rate signal is extracted. At thismoment, in the detector circuit, a signal component (an undesired signalcomponent) is generated due to the oscillation at each detectorelectrodes 3, 4, 7, and 8. At the detector electrodes 3, 4 disposedsymmetrically about the driver electrodes 1, 2, undesired signalcomponents having the same amplitudes and the phases inverted to eachother are generated but canceled in the detector electrodes 3, 4. At thedetector electrodes 7, 8 disposed symmetrically about the driverelectrode 5, undesired signal components having the same amplitudes andphases are generated but canceled in the differential amplifier 44receiving the components. The synchronously detected output of thedetector 46 is transferred to an LPF 47 where it is DC-converted, and isdetected as the angular rate signal as the DC component.

According to Embodiment 1, the electrodes for applying a driving voltageis more than that of the conventional arrangement, and the efficiency ofthe driving operation increases to 1.5 times.

The driver electrode 5 and monitor electrode 6 are mounted on the firstmain surface and the second main surface of the arm 10 b, respectively,in the embodiment. They may be switched in the location, and a signalsupplied to the newly-disposed driver electrode may accordingly beinverted.

In the embodiment, the detector electrodes 3 and 4 are mounted on theouter and inner surfaces of the arm 10 a, respectively, however they maybe grounding electrodes.

In the embodiment 1, to detect the angular rate is described. A angularrate applied along the Z-axis of the arms 10 a, 10 b has the influencereduced or eliminated by the detector electrodes 3, 4, 7, and 8.

Embodiment 2

FIG. 5 is a schematic view of the arrangement of electrodes on arms ofan angular rate sensor according to Embodiment 2 of the presentinvention. In FIG. 5, like components are denoted by like numerals asthose illustrated in FIGS. 1, 2, 3, and 4 and will be described in nomore detail but different components. In FIG. 5, reference numeral 50denotes a driver electrode disposed on an outer portion of the firstmain surface of the arm 10 b. Reference numeral 51 denotes a driverelectrode disposed on an outer portion of the second main surface of thearm 10 b. Reference numeral 52 denotes a monitor electrode disposed onan inner portion of the first main surface of the arm 1 b. Referencenumeral 53 denotes a monitor electrode disposed on an inner portion ofthe second main surface of the arm 10 b.

An operation of the angular rate sensor of Embodiment 2 will beexplained. To the driver electrodes 1, 51 and the driver electrodes2,50, two different alternating currents having different phases in 180degrees from each other are supplied from the driving source 9,respectively, hence producing a certain tuning fork oscillation.

According to Embodiment 2, the electrodes for applying a driving voltageis more than that of the conventional sensor, and the efficiency of thedriving operation increases to 1.7 times.

In Embodiment 2, a coupling capacitance component contained in anundesired signal component in the driving signal received by thedetector electrodes is eliminated.

The driver electrode 51 and monitor electrode 53 are mounted on theouter and inner portions of the second main surface of the arm 10 b,respectively, in Embodiment 2. The locations of them may be switchedover with equal effects.

The monitor electrodes 52, 53 are mounted on the outer portion of thefirst main surface and the inner surface of the second main surface ofthe arm 10 b, respectively, in Embodiment 2. Each of them may be agrounding electrode.

Embodiment 3

FIG. 6 is a schematic view of the arrangement of electrodes on arms ofan angular rate sensor according to Embodiment 3 of the presentinvention. In FIG. 6, like components are denoted by like numerals asthose illustrated in FIGS. 1, 2, 3, and 4 and will be described in nomore detail but different components. In FIG. 6, reference numeral 54denotes a driver electrode provided on a portion of the outer surfacecloser to the first main surface of the arm 10 a. Reference numeral 55denotes a driver electrode provided on a portion of the outer surfacecloser to the second main surface of the arm 10 a.

An operation of the angular rate sensor of Embodiment 3 will beexplained. To the driver electrodes 1, 55 and driver electrodes 2, 5,and 54, alternating currents having a different phase in 180 degreesfrom each other are applied from the driving source 9, respectively,hence producing a tuning fork oscillation.

According to Embodiment 3, the electrodes for applying a driving voltageis more than that of the conventional sensor, and the intensity ofelectric field applied to a region of the arm 10 a close to the outersurface is higher. Accordingly, the efficiency of the driving operationincreases to 2.5 times.

In Embodiment 3, a coupling capacitance component contained in anundesired signal component in the driving signal received by thedetector electrodes is eliminated.

The driver electrode 5 and monitor electrode 6 are mounted on the firstmain surface and the second main surface of the arm 10 b, respectively,in Embodiment 2. They may be switched over in the location, and thealternating currents applied to the respective driver electrodes mayaccordingly be opposite in the polarity to those of this arrangement.

The monitor electrodes 54, 55 are mounted on the outer surface of thearm 10 a in Embodiment 3, and the detector electrode 4 is mounted on theinner surface of the arm. The electrodes 54, 55 may be switched overwith the detector electrode 4 in the location.

The detector electrode 4 is mounted on the inner surface of the arm 10 ain the embodiment, and however may be a grounding electrode.

The driver electrode 5 is mounted on the first main surface of the arm10 b in the embodiment, and however may be a grounding electrode. Thisincreases the efficiency of the driving operation to 2.0 times greaterthan that of the conventional sensor. Simultaneously, as the driverelectrodes 1, 2 are equally spaced from the corresponding detectorelectrodes 7, 8, undesired coupling capacitance components generated onthe detector electrode 7, 8 are offset to each other, hence an influenceof a noise is eliminated.

Embodiment 4

FIG. 7 is a schematic view of the arrangement of electrodes on arms ofan angular rate sensor according to Embodiment 4 of the presentinvention. In FIG. 7, like components are denoted by like numerals asthose illustrated in FIG. 6 and will be described in no more detail butdifferent components. In FIG. 7, reference numeral 56 denotes a driverelectrode provided on a portion of the inner surface closer to the firstmain surface of the arm 10 a. Reference numeral 57 denotes a driverelectrode provided on a portion of the inner surface closer to thesecond main surface of the arm 10 a.

An operation of the angular rate sensor of Embodiment 4 will beexplained. To the driver electrodes 1, 55, and 57 and driver electrodes2, 5, 54, and 56, alternating currents having different phases of 180degrees from each other are supplied, respectively, hence producing atuning fork oscillation.

According to Embodiment 4, the number of electrodes for applying adriving voltage is more than that of the conventional sensor, and theintensity of electric field applied to the arm 10 a is higher than theconventional sensor. Accordingly, the efficiency of the drivingoperation increases to 3.2 times greater.

In Embodiment 4, a coupling capacitance component contained in anundesired signal component in the driving signal received by thedetector electrodes is canceled.

The driver electrode 5 and monitor electrode 6 are mounted on the firstand second main surfaces of the arm 10 b, respectively, in theembodiment. They may be switched over in the location, and thealternating currents applied to the respective driver electrodes mayaccordingly be opposite in the polarity to those of this arrangement.

The driver electrode 5 mounted on the first main surface of the arm 10 bmay be a grounding electrode. This increases the efficiency of thedriving operation to 2.7 times greater than that of the conventionalsensor. Simultaneously, as the driver electrodes 1, 2 are equally spacedfrom the corresponding detector electrodes 7, 8, undesired couplingcapacitance components developed on the detector electrode 7, 8 isoffset to each other, hence an influence of a noise is eliminated.

Embodiment 5

FIG. 8 is a schematic view of the arrangement of electrodes on arms ofan angular rate sensor according to Embodiment 5 of the presentinvention. In FIG. 8, like components are denoted by like numerals asthose illustrated in FIG. 6 and will be described in no more detail butdifferent components. In FIG. 8, reference numeral 58 denotes a driverelectrode provided on a portion of the first main surface closer to theouter surface of the arm 10 a. Reference numeral 59 denotes a driverelectrode provided on a portion of the second main surface closer to theouter surface of the arm 10 a. Reference numeral 60 denotes a monitorelectrode provided on a portion of the first main surface closer to theinner surface of the arm 10 a. Reference numeral 61 denotes a monitorelectrode provided on a portion of the second main surface closer to theinner surface of the arm 10 a. Reference numeral 62 denotes a driverelectrode provided on a portion of the outer surface closer to the firstmain surface of the arm 10 b. Reference numeral 63 denotes a driverelectrode provided on a portion of the outer surface closer to thesecond main surface of the arm 10 b.

An operation of the angular rate sensor of Embodiment 5 will beexplained. To the driver electrodes 58, 55, 62, and 51 and the driverelectrodes 59, 54, 50, and 63, alternating currents having differentphases of 180 degrees from each other are applied from the drivingsource 9, respectively, hence producing a tuning fork oscillation.

In the embodiment, the intensity of electric field at regions of thearms 10 a and 10 b close to the outer surface is higher than that of theconventional sensor, as shown in FIG. 8. Accordingly, the efficiency ofthe driving operation increases to 3.4 times greater. As the number ofmonitor electrodes increases, a charge to be monitored increases hencedeclining the ratio of a noise to the input signal received by the AGCcircuit 42.

In the embodiment, the drivers electrodes 58, 54, 55, 59, 50, 62, 63,and 51 are fairly spaced from the detector electrodes 4, 7 on the arms10 a, 10 b. An influence of an undesired coupling capacitance componentto the detector electrodes 4, 7 commonly-connected is reduced. Also,even if a small intensity of the electric field is applied to thedetector electrodes 4, 7 from the driver electrodes 58, 54, 55, 59, 50,62, 63, and 51, the undesired coupling capacitance component is offsetto each other.

In the embodiment, the driver electrodes 54, 55 are mounted on the outersurface of the arm 10 a. The detector electrode 4 is mounted on theinner surface of the arm. The driver electrode 58 and monitor electrode60 are mounted on the first main surface of the arm. And the driverelectrode 59 and monitor electrode 61 are mounted on the second mainsurface of the arm. The driver electrodes 54, 55 and detector electrode4 may be switched over in the location, the driver electrode 58 andmonitor electrode 60 may simultaneously be switched over in thelocation, and the driver electrode 59 and monitor electrode 61 may besimultaneously switched over in the location. In this case, an angularrate is detected with the differential signal of the detector electrodes4 and 7.

In the embodiment, the driver electrodes 62, 63 are mounted on the outersurface of the arm 10 b. The detector electrode 7 is mounted on theinner surface of the arm. The driver electrode 50 and monitor electrode52 are mounted on the first main surface. The driver electrode 51 andmonitor electrode 53 are mounted on the second main surface of the arm10 b. The locations of the driver electrodes 62, 63 and that of thedetector electrode 7 may be switched over, the location of the driverelectrode 50 and that of the monitor electrode 52 may be simultaneouslyswitched over, and the location of the driver electrode 51 and that ofthe monitor electrode 53 may be simultaneously switched over. In thiscase, an angular rate is detected from the differential signal of thedetector electrodes 4 and 7.

In the embodiment, the driver electrodes 54, 55 are mounted on the outersurface of the arm 10 a. The detector electrode 4 is mounted on theinner surface of the arm. The driver electrode 58 and monitor electrode60 are mounted on the first main surface of the arm. The driverelectrode 59 and monitor electrode 61 are mounted on the second mainsurface of the arm. The driver electrodes 62, 63 are mounted on theouter surface of the arm 10 b. The detector electrode 7 is mounted onthe inner surface of the arm. The driver electrode 50 and monitorelectrode 52 are mounted on the first main surface of the arm. Thedriver electrode 51 and monitor electrode 53 are mounted on the secondmain surface of the arm. The locations of the driver electrode 54, 55and that of the detector electrode 4 may be switched over, the locationof the driver electrode 58 and that of the monitor electrode 60 may besimultaneously switched over, the location of the driver electrode 59and that of the monitor electrode 61 may be simultaneously switchedover, and the locations of the driver electrodes 62, 63 and that of thedetector electrode 7 may be simultaneously switched over, the locationof the driver electrode 50 and that of the monitor electrode 52 may besimultaneously switched over, the location of the driver electrode 51and that of the monitor electrode 53 may be simultaneously switchedover. In this case, an angular rate is detected, similarly to Embodiment5, with the detector electrodes 4 and 7 connected to a common port.

In the embodiment, the monitor electrodes 60, 61 are mounted on thefirst and second main surfaces of the arm 10 a, respectively, while themonitor electrodes 52 and 53 are mounted on the first and second mainsurfaces of the other arm 10 b, respectively. Alternatively, two of themonitor electrodes 52, 53, 60, and 61 are assigned as the monitorelectrodes, and the other two may be grounding electrodes. Thisarrangement permits the grounding electrodes to be disposed between thedriver electrode and the detector electrode, thus reducing an undesiredcoupling capacitance component transferred from the driver electrode tothe detector electrode.

Embodiment 6

FIG. 9 is a schematic view of the arrangement of electrodes on arms ofan angular rate sensor according to Embodiment 6 of the presentinvention. In FIG. 9, like components are denoted by like numerals asthose illustrated in FIGS. 3 and 8 and will be described in no moredetail but different components.

An operation of the angular rate sensor of Embodiment 6 will beexplained. To the driver electrodes 1, 55, 62, and 51 and the driverelectrodes 52, 54, 50, and 63, alternating currents having a differentphase of 180 degrees from each other are applied from the driving source9, respectively, hence producing a tuning fork oscillation.

According to Embodiment 6, the intensity of electric field at regions ofthe arms 10 a and 10 b close to the outer surface is higher than that ofthe conventional sensor, as shown in FIG. 9. Accordingly, the efficiencyof the driving operation increases to 3.7 times greater.

Also, a coupling capacitance component in an undesired signal componentof the signal received by the detector electrode 4 of the arm 10 a iseliminated. As the driver electrodes 50, 51, 62, and 63 are fairlyspaced from the detector electrode 7 of the arm 10 b, an influence ofthe coupling capacitance component on the detector electrode 7 isreduced. Furthermore, even when a small electric field generated by thedriver electrodes 50, 51, 62, and 63 is applied to the detectorelectrode 7, the coupling capacitance component is canceled on thedetector electrode 7.

In the embodiment, the driver electrodes 54 and 55 are mounted on theouter surface of the arm 10 a. The detector electrode 4 is mounted onthe inner surface of the arm. The driver electrode 1 is mounted on thefirst main surface. The driver electrode 2 is mounted on the second mainsurface of the arm. The locations of the driver electrodes 54, 55 andthat of the detector electrode 4 may be switched over. In this case, theangular rate is detected from a differential signal of the detectorelectrodes 4 and 7.

In the embodiment, the driver electrodes 62, 63 are mounted on the outersurface of the arm 10 b. The detector electrode 7 is mounted on theinner surface of the arm. The driver electrode 50 and monitor electrode52 are mounted on the first main surface of the arm. The driverelectrode 51 and monitor electrode 53 are mounted on the second mainsurface of the arm. The locations of the driver electrodes 62, 63 andthat of the detector electrode 7 may be switched over, the location ofthe driver electrode 50 and that of the monitor electrode 52 may besimultaneously switched over, the location of the driver electrode 51and that of the monitor electrode 53 may be simultaneously switchedover. In this case, the angular rate signal is calculated from thedifferential signal of the detector electrodes 4 and 7.

In the embodiment, the driver electrodes 54 and 55 are mounted on theouter surface of the arm 10 a. The detector electrode 4 is mounted onthe inner surface of the arm. The driver electrode 1 is mounted on thefirst main surface of the arm. The driver electrode 2 is mounted on thesecond main surface of the arm. The driver electrodes 62 and 63 aremounted on the outer surface of the arm 10 b. The detector electrode 7is mounted on the inner surface of the arm 10 b. The driver electrode 50and monitor electrode 52 are mounted on the first surface of the arm 10b. The driver electrode 51 and monitor electrode 53 are mounted on thesecond main surface of the arm 10 b. The locations of the driverelectrode 54, 55 and that of the detector electrode 4 may be switchedover, the locations of the driver electrodes 62, 63 and that of thedetector electrode 7 may be simultaneously switched over, the locationof the driver electrode 50 and that of the monitor electrode 52 may besimultaneously switched over, the location of the driver electrode 51and that of the monitor electrode 53 may be simultaneously switchedover. In this case, the angular rate is detected with the detectorelectrodes 4 and 7 connected to a common port, similarly to Embodiment6.

Embodiment 7

FIG. 10 is a schematic view of the arrangement of electrodes on arms ofan angular rate sensor according to Embodiment 7 of the presentinvention. In FIG. 10, like components are denoted by like numerals asthose illustrated in FIGS. 7 and 9 and will be described in no moredetail but different components. In FIG. 10, reference numeral 64denotes a driver electrode provided on a portion of the inner surfacecloser to the first main surface of the arm 10 b. Reference numeral 65denotes a detector electrode provided on a portion of the inner surfacecloser to the second main surface of the arm 10 b. Reference numeral 71denotes a detector electrode provided on a portion of the outer surfacecloser to the second main surface of the arm 10 a. Reference numeral 72denotes a detector electrode provided on a portion of the inner surfacecloser to the second main surface of the arm 10 a. Reference numeral 73denotes a detector electrode provided on a portion of the outer surfacecloser to the second main surface of the arm 10 b.

An operation of the angular rate sensor of Embodiment 7 will beexplained. To the driver electrodes 1, 64, and 62 and the driverelectrodes 2, 5, 54, and 56, alternating currents having a differentphase of 180 degrees from each other are applied from the driving source9 in Embodiment 7, hence producing a tuning fork oscillation.

According to Embodiment 7, the electrodes for applying a driving voltageare more than those of the conventional sensor, and the intensity ofelectric field at regions of the arms 10 a and 10 b close to the firstmain surface is higher. Accordingly, the efficiency of the drivingoperation increases to 3.2 times greater.

Also, a coupling capacitance component in an undesired signal componentin the driving signal received by the detector electrode is eliminated.

Embodiment 8

FIGS. 11, 13 and FIGS. 12, 14 are perspective views of a tuning forkoscillator of an angular sensor, seen from the first and second mainsurfaces, respectively, according to Embodiment 8 of the presentinvention. Throughout FIGS. 11, 12, 13, and 14, like components aredenoted by like numerals as those illustrated in FIGS. 1, 2, and 3 andwill be explained in no more detail but different components. In FIG.11, reference numeral 1 a denotes an electrode extension of theelectrode 1 provided on the first main surface of an arm 10 a andarranged extending into a base 20 c. Reference numeral 5 a denotes anelectrode extension of the electrode 5 provided on the first mainsurface of a arm 10 b and arranged extending into a base 20 c. In FIG.12, reference numeral 2 a denotes an electrode extension of theelectrode 2 provided on the second main surface of an arm 10 a andarranged extending into a base 30 c. Reference numeral 6 a denotes anelectrode extension of the electrode 6 provided on the second mainsurface of an arm 10 b and arranged extending into a base 30 c.

As each driver electrode of Embodiment 8 extends into the base 10 clonger than that of the conventional sensor, the total area of theelectrodes increases thus improving the efficiency of the drivingoperation.

Also, as shown in FIGS. 13 and 14, reference numeral 8 a denotes anelectrode extension of the detector electrode 8 provided on the outersurface of the arm 10 b and arranged extending into the base 10 c.Reference numeral 3 a denotes an electrode extension of the detectorelectrode 3 provided on the outer surface of the arm 10 a and arrangedextending into the base 10 c.

As each detector electrode of Embodiment 8 extends into the base 10 clonger than that of the conventional sensor, the total area of theelectrodes increases thus improving the efficiency of the detectingoperation.

In the embodiment, the electrodes on the arms 10 a and 10 b describedabove extends into the base 10 c. The separated electrodes on the arms,such as shown in any of Embodiments 2 to 7, may extend into the base 10c.

Industrial Applicability

As set forth above, an angular rate sensor according to the presentinvention includes a tuning fork oscillator having a first oscillatormember of a single crystalline piezoelectric material composed of atleast two arms and a base joining the two arms and a second oscillatormember of the single crystalline piezoelectric material having asubstantially identical shape to the first oscillator member. The twooscillators are bonded directly to each other in the direction of thecrystallographic axis and the thickness so that opposite polarities of apiezoelectric effect my be developed along the widthwise direction ofthe oscillators. The tuning fork oscillator includes at least two armsand a base. The sensor further includes: first, second, third, andfourth electrodes provided on a first main surface, a second mainsurface, an outer surface, and an inner surface of one of the two armsof the tuning fork oscillator, respectively; a fifth electrode providedon either a first main surface or a second main surface of the other armof the tuning fork oscillator; and sixth and seventh electrodes providedon an inner surface and an outer surface of the other arm of the tuningfork oscillator, respectively. When the fifth electrode is provided onthe first main surface, a driving voltage is applied to the second andfifth electrodes at the same polarity, and applied to the firstelectrode at the reverse polarity against the second and fifthelectrodes. When the fifth electrode is provided on the second mainsurface, a driving voltage is applied to the second and fifth electrodesat the reverse polarity against each other, and applied to the firstelectrode at the same polarity as the fifth electrode. The angular ratesensor includes more electrodes to which the driving voltage is appliedand has the efficiency of a driving operation improved.

What is claimed is:
 1. An angular rate sensor comprising: a tuning forkoscillator having at least two arms and a base, including: a firstoscillator member of a single crystalline piezoelectric material havingat least two arms and a base joining the two arms; and a secondoscillator member of the single crystalline piezoelectric materialhaving a shape substantially identical to a shape of said firstoscillator member, said first and second oscillator members being bondeddirectly to each other in a direction of a thickness and in a directionof a crystallographic axis so that opposite polarities of apiezoelectric effect may be developed along a widthwise direction ofsaid first and second oscillator members; first, second, third, andfourth electrodes provided on a first main surface, a second mainsurface, an outer surface, and an inner surface of one of the arms ofsaid tuning fork oscillator, respectively; a fifth electrode provided onone of first and second main surfaces of other arm of the arms of saidtuning fork oscillator; and sixth and seventh electrodes provided oninner and outer surfaces of the other arm of said tuning forkoscillator, respectively; wherein, when said fifth electrode is providedon the first main surface, a driving voltage is applied to said secondand fifth electrodes at a polarity identical to each other and appliedto said first electrode at a polarity opposite to said second and fifthelectrodes; and wherein, when said fifth electrode is provided on thesecond main surface, a driving voltage is applied to said second andfifth electrodes at polarities opposite to each other and applied tosaid first electrode at a polarity identical to said fifth electrode. 2.The angular rate sensor according to claim 1, wherein said third andseventh electrodes are connected to a common port, said fourth and sixthelectrodes are connected to another common port, and a detection signalis detected from a differential signal between the common ports.
 3. Anangular rate sensor comprising: a tuning fork oscillator having at leasttwo arms and a base, including: a first oscillator member of a singlecrystalline piezoelectric material having at least two arms and a basejoining the two arms; and a second oscillator member of the singlecrystalline piezoelectric material having a shape substantiallyidentical to a shape of said first oscillator member, said first andsecond oscillator members being bonded directly to each other in adirection of a thickness and in a direction of a crystallographic axisso that opposite polarities of a piezoelectric effect may be developedalong a widthwise direction of said first and second oscillator members;first, second, third, and fourth electrodes provided on a first mainsurface, a second main surface, an outer surface, and an inner surfaceof one of the arms of said tuning fork oscillator, respectively; fifthand sixth electrodes provided on first and second main surfaces of otherarm of the arms of said tuning fork oscillator, respectively, said fifthand sixth electrodes being provided on portions close to one of outerand inner surfaces of the other arm, respectively; and a seventhelectrode provided on a surface of the other arm of said tuning forkoscillator; wherein, when said fifth and sixth electrodes are providedon the portions close to the outer surface of the other arm,respectively, said seventh electrode is provided on the outer surface;wherein, when said fifth and sixth electrodes are provided on theportions close to the inner surface of the other arm, respectively, saidseventh electrode is provided on the inner surface; and wherein adriving voltage is applied to said first and sixth electrodes at apolarity identical to each other and applied to said second and fifthelectrodes at a polarity opposite to said first and sixth electrodes. 4.The angular rate sensor according to claim 3, further comprising aneighth electrode provided on a surface opposite to the surface of theother arm of said tuning fork oscillator on which said seventh electrodeis provided; wherein, when said seventh electrode is provided on theouter surface, said fourth and eight electrodes are connected to acommon port, said third and seventh electrodes are connected to anothercommon port, and a detection signal is detected from a differentialsignal between the common ports; and wherein, when said seventhelectrode is provided on the inner surface, said third and eightelectrodes are connected to a common port, said fourth and seventhelectrodes are connected to another common port, and a detection signalis detected from a differential signal between the common ports.
 5. Anangular rate sensor comprising: a tuning fork oscillator having at leasttwo arms and a base, including: a first oscillator member of a singlecrystalline piezoelectric material having at least two arms and a basejoining the two arms; and a second oscillator member of the singlecrystalline piezoelectric material having a shape substantiallyidentical to a shape of said first oscillator member, said first andsecond oscillator members being bonded directly to each other in adirection of a thickness and in a direction of a crystallographic axisso that opposite polarities of a piezoelectric effect may be developedalong a widthwise direction of said first and second oscillator members;first, second, third, and fourth electrodes provided on a first mainsurface, a second main surface, an outer surface, and an inner surfaceof one of the arms of said tuning fork oscillator, respectively; andfifth, sixth, seventh, and eighth electrodes provided on a first mainsurface, a second main surface, an outer surface, and an inner surfaceof other arm of the arms of said tuning fork oscillator, respectively;wherein, when said fifth electrode is provided on a portion close to theouter surface of the other arm, said sixth electrode is provided on aportion close to the inner surface of the other arm; wherein, when saidfifth electrode is provided on a portion close to the inner surface ofthe other arm, said sixth electrode is provided on a portion close tothe outer surface of the other arm; and wherein a driving voltage isapplied to said first and sixth electrodes at a polarity identical toeach other and applied to said second and fifth electrodes at a polarityopposite to said first and sixth electrodes.
 6. The angular rate sensoraccording to claim 5, wherein a detection signal is detected from adifferential signal between said third and fourth electrodes.
 7. Anangular rate sensor comprising: a tuning fork oscillator having at leasttwo arms and a base, including: a first oscillator member of a singlecrystalline piezoelectric material having at least two arms and a basejoining the two arms; and a second oscillator member of the singlecrystalline piezoelectric material having a shape substantiallyidentical to a shape of said first oscillator member, said first andsecond oscillator members being bonded directly to each other in adirection of a thickness and in a direction of a crystallographic axisso that opposite polarities of a piezoelectric effect may be developedalong a widthwise direction of said first and second oscillator members;first and second electrodes provided on first and second main surfacesof one of the arms of said tuning fork oscillator, respectively; thirdand fourth electrodes provided on one of outer and inner surfaces of theone of the arms, said third and fourth electrodes being provided on aportion close to said first electrode and a portion close to said secondelectrode, respectively; and a fifth electrode provided on a surfaceopposite to the surface on which said third and fourth electrodes areprovided; wherein a driving voltage is applied to said first and fourthelectrodes at a polarity identical to each other and applied to saidsecond and third electrodes at a polarity opposite to said first andfourth electrodes.
 8. The angular rate sensor according to claim 7,further comprising sixth and seventh electrodes provided on inner andouter surfaces of the other arm of said tuning fork oscillator,respectively; wherein, when said fifth electrode is provided on theinner surface of the one of the arms, a detection signal is detectedfrom a differential signal between said sixth and seventh electrodes, orsaid fifth and sixth electrodes are connected to a common port, and adetection signal is detected from a differential signal between thecommon port and said seventh electrode; and wherein, when said fifthelectrode is provided on the outer surface of the one of the arms, adetection signal is detected from a differential signal between saidsixth and seventh electrodes, or said fifth and seventh electrodes areconnected to a common port, and a detection signal is detected from adifferential signal between the common port and said sixth electrode. 9.The angular rate sensor according to claim 7, further comprising: asixth electrode provided on one of first and second main surfaces of theother arm of said tuning fork oscillator; and seventh and eighthelectrodes provided on inner and outer surfaces of the other arm,respectively; wherein, when said sixth electrode is provided on thefirst main surface, a driving voltage is applied to said first and sixthelectrodes at polarities opposite to each other; and wherein, when saidsixth electrode is provided on the second main surface, a drivingvoltage is applied to said first and sixth electrodes at a polarityidentical to each other.
 10. The angular rate sensor according to claim9, wherein: when said fifth electrode is provided on the inner surfaceof the one of the arms, a detection signal is detected from adifferential signal between said seventh and eighth electrodes, or saidfifth and seventh electrodes are connected to a common port, and adetection signal is detected from a differential signal between thecommon port and said eighth electrode; and when said fifth electrode isprovided on the outer surface of the one of the arms, a detection signalis detected from a differential signal between said seventh and eighthelectrodes, or said fifth and eight electrodes are connected to a commonport, and a detection signal is detected from a differential signalbetween the common port and said seventh electrode.
 11. An angular ratesensor comprising: a tuning fork oscillator having at least two arms anda base, including: a first oscillator member of a single crystallinepiezoelectric material having at least two arms and a base joining thetwo arms; and a second oscillator member of the single crystallinepiezoelectric material having a shape substantially identical to a shapeof said first oscillator member, said first and second oscillatormembers being bonded directly to each other in a direction of athickness and in a direction of a crystallographic axis so that oppositepolarities of a piezoelectric effect may be developed along a widthwisedirection of said first and second oscillator members; first and secondelectrodes provided on first and second main surfaces of one of the armsof said tuning fork oscillator, respectively; third and fourthelectrodes provided on an outer surface of the one of the arms, saidthird and fourth electrodes being provided on a portion close to saidfirst electrode and a portion close to said second electrode,respectively; and fifth and sixth electrodes provided on an innersurface of the one of the arms, said fifth and sixth electrodes beingprovided on a portion close to said first electrode and a portion closeto said second electrode, respectively; wherein a driving voltage isapplied to said first, fourth, and sixth electrodes at a polarityidentical to one another and applied to said second, third, and fifthelectrodes at a polarity opposite to said first, fourth, and sixthelectrodes.
 12. The angular rate sensor according to claim 11, furthercomprising seventh and eighth electrodes provided on inner and outersurfaces of the other arm of said tuning fork oscillator, respectively,wherein a detection signal is detected from a differential signalbetween said seventh and eighth electrodes.
 13. The angular rate sensoraccording to claim 11, further comprising: a seventh electrode providedon one of first and second main surfaces of other arm of the arms ofsaid tuning fork oscillator; and eighth and ninth electrodes provided oninner and outer surfaces of the other arm, respectively; wherein, whensaid seventh electrode is provided on the first main surface, a drivingvoltage is applied to said first and seventh electrodes at polaritiesopposite to each other; and wherein, when said seventh electrode isprovided on the second main surface, a driving voltage is applied tosaid first and seventh electrodes at a polarity identical to each other.14. The angular rate sensor according to claim 13, wherein a detectionsignal is detected from a differential signal between said eighth andninth electrodes.
 15. An angular rate sensor comprising: a tuning forkoscillator having at least two arms and a base, including: a firstoscillator member of a single crystalline piezoelectric material havingat least two arms and a base joining the two arms; and a secondoscillator member of the single crystalline piezoelectric materialhaving a shape substantially identical to a shape of said firstoscillator member, said first and second oscillator members being bondeddirectly to each other in a direction of a thickness and in a directionof a crystallographic axis so that opposite polarities of apiezoelectric effect may be developed along a widthwise direction ofsaid first and second oscillator members; first and second electrodesprovided on first and second main surfaces of one of the arms of saidtuning fork oscillator, respectively, said first and second electrodesbeing provided on portions close to an outer surface of the one of thearms, respectively; third and fourth electrodes provided on the outersurface of the one of the arms, said third and fourth electrodes beingprovided on a portion close to the first main surface of the one of thearms and a portion close to the second main surface of the one of thearms, respectively; fifth and sixth electrodes provided on first andsecond main surfaces of other arm of the arms of said tuning forkoscillator, said fifth and sixth electrodes being provided on portionsclose to an outer surface of the other arm of said tuning forkoscillator, respectively; and seventh and eighth electrodes provided onthe outer surface of the other arm, said seventh and eighth electrodesbeing provided on a portion close to the first main surface of the otherarm and a portion close to the second main surface of the of the arm,respectively; wherein a driving voltage is applied to said first,fourth, sixth, and seventh electrodes at a polarity identical to oneanother and applied to said second, third, fifth, and eighth electrodesat a polarity opposite to said first, fourth, sixth, and seventhelectrodes.
 16. The angular rate sensor, according to claim 7, furthercomprising electrodes provided on inner surfaces of the arms of saidtuning fork oscillator, respectively, wherein said electrodes beingconnected to a common port, and a detection signal is detected from thecommon port.
 17. An angular rate sensor comprising: a tuning forkoscillator having at least two arms and a base, including: a firstoscillator member of a single crystalline piezoelectric material havingat least two arms and a base joining the two arms; a second oscillatormember of the single crystalline piezoelectric material having a shapesubstantially identical to a shape of said first oscillator member, saidfirst and second oscillator members being bonded directly to each otherin a direction of a thickness and in a direction of a crystallographicaxis so that opposite polarities of a piezoelectric effect may bedeveloped along a widthwise direction of said first and secondoscillator members; first and second electrodes provided on first andsecond main surfaces of one of the arms of said tuning fork oscillator,respectively, said first and second electrodes being provided onportions close to an inner surface of the one of the arms, respectively;third and fourth electrodes provided on the inner surface of the one ofthe arms, said third and fourth electrodes being provided on a portionclose to the first main surface of the one of the arms and a portionclose to the second main surface of the one of the arms, respectively;fifth and sixth electrodes provided on first and second main surfaces ofother arm of the arms of said tuning fork oscillator, respectively, saidfifth and sixth electrodes being provided on portions close to an innersurface of the other arm, respectively; and seventh and eighthelectrodes provided on the inner surface of the other arm, said seventhand eighth electrodes being provided on a portion close to the firstmain surface of the other arm and a portion close to the second mainsurface of the other arm, respectively; wherein a driving voltage isapplied to said first, fourth, sixth, and seventh electrodes at apolarity identical to one another and applied to said second, third,fifth, and eighth electrodes at a polarity opposite to said first,fourth, sixth, and seventh electrodes.
 18. The angular rate sensoraccording to claim 17, further comprising electrodes provided on outersurfaces of the arms of said tuning fork oscillator, respectively,wherein said electrodes are connected to a common port, and a detectionsignal is detected from the common port.
 19. An angular rate sensorcomprising: a tuning fork oscillator having at least two arms and abase, including: a first oscillator member of a single crystallinepiezoelectric material having at least two arms and a base joining thetwo arms; and a second oscillator member of the single crystallinepiezoelectric material having a shape substantially identical to a shapeof said first oscillator member, said first and second oscillatormembers being bonded directly to each other in a direction of athickness and in a direction of a crystallographic axis so that oppositepolarities of a piezoelectric effect may be developed along a widthwisedirection of said first and second oscillator members; first and secondelectrodes provided on first and second main surfaces of one of the armsof said tuning fork oscillator, respectively, said first and secondelectrodes being provided on portions close to an outer surface of theone of the arms, respectively; third and fourth electrodes provided onthe outer surface of the one of the arms, said third and fourthelectrodes being provided on a portion close to the first main surfaceof the one of the arms and a portion close to the second main surface ofthe one of the arms, respectively; fifth and sixth electrodes providedon first and second main surfaces of other arm of the arms of saidtuning fork oscillator, respectively, said fifth and sixth electrodesbeing provided on portions close to an inner surface of the other arm,respectively; and seventh and eighth electrodes provided on the innersurface of the other arm, said seventh and eighth electrodes beingprovided on a portion close to the first main surface of the other armand a portion close to the second main surface of the other arm,respectively; wherein a driving voltage is applied to said first,fourth, sixth, and seventh electrodes at a polarity identical to oneanother and applied to said second, third, fifth, and eighth electrodesat a polarity opposite to said first, fourth, sixth, and seventhelectrodes.
 20. The angular rate sensor according to claim 19, furthercomprising: a ninth electrode provided on an inner surface of the one ofthe arms of said tuning fork oscillator; and a tenth electrode providedon an outer surface of the other arm, wherein a detection signal isdetected from a differential signal between said ninth and tenthelectrodes.
 21. An angular rate sensor comprising: a tuning forkoscillator having at least two arms and a base, including: a firstoscillator member of a single crystalline piezoelectric material havingat least two arms and a base joining the two arms; and a secondoscillator member of the single crystalline piezoelectric materialhaving a shape substantially identical to a shape of said firstoscillator member, said first and second oscillator members being bondeddirectly to each other in a direction of a thickness and in a directionof a crystallographic axis so that opposite polarities of apiezoelectric effect may be developed along a widthwise direction ofsaid first and second oscillator members; first and second electrodesprovided on first and second main surfaces of one of the arms of saidtuning fork oscillator, respectively, said first and second electrodesbeing provided on portions close to an inner surface of the one of thearms, respectively; third and fourth electrodes provided on the innersurface of the one of the arms, said third and fourth electrodes beingprovided on a portion close to the first main surface of the one of thearms and a portion close to the second main surface of the one of thearms, respectively; fifth and sixth electrodes provided on first andsecond main surfaces of other arm of the arms of said tuning forkoscillator, respectively, said fifth and sixth electrodes being providedon portions close to an outer surface of the other arm, respectively;and seventh and eighth electrodes provided on the outer surface of theother arm, said seventh and eighth electrodes being provided on aportion close to the first main surface of the other arm and a portionclose to the second main surface of the other arm, respectively; whereina driving voltage is applied to said first, fourth, sixth, and seventhelectrodes at a polarity identical to one another and applied to saidsecond, third, fifth, and eighth electrodes at a polarity opposite tosaid first, fourth, sixth, and seventh electrodes.
 22. The angular ratesensor according to claim 21, further comprising: a ninth electrodeprovided on an outer surface of the one of the arms of said tuning forkoscillator; and a tenth electrode provided on an inner surface of theother arm, wherein a detection signal is detected from a differentialsignal between said ninth and tenth electrodes.
 23. The angular ratesensor according to claim 15, further comprising four monitor electrodesprovided on remaining portions of the first and second main surfaces ofthe arms of said tuning fork oscillator, respectively.
 24. The angularrate sensor according to claim 16, further comprising: two groundingelectrodes provided on remaining portions of the first and second mainsurfaces of the one of the arms of said tuning fork oscillator,respectively; and two monitor electrodes provided on remaining portionsof the first and second main surfaces of the other arm.
 25. An angularrate sensor comprising: a tuning fork oscillator having at least twoarms and a base, including: a first oscillator member of a singlecrystalline piezoelectric material having at least two arms and a basejoining the two arms; and a second oscillator member of the singlecrystalline piezoelectric material having a shape substantiallyidentical to a shape of said first oscillator member, said first andsecond oscillator members being bonded directly to each other in adirection of a thickness and in a direction of a crystallographic axisso that opposite polarities of a piezoelectric effect may be developedalong a widthwise direction of said first and second oscillator members;first and second electrodes provided on first and second main surfacesof one of the arms of said tuning fork oscillator, respectively; thirdand fourth electrodes provided on one of outer and inner surfaces of theone of the arms, said third and fourth electrodes being provided on aportion close to said first electrode and a portion close to said secondelectrode, respectively; a fifth electrode provided on one of the innerand outer surfaces of the one of the arms, said fifth electrode beingprovided on a surface opposite to the surface on which said third andfourth electrodes are provided; sixth and seventh electrodes provided onfirst and second main surfaces of other arm of said arms of the tuningfork oscillator, respectively, said sixth and seventh electrodes beingprovided on portions close to an outer surface of the other arm,respectively; and eighth and ninth electrodes provided on the outersurface of the other arm, said eighth and ninth electrodes beingprovided on a portion close to said sixth electrode and a portion closeto said seventh electrode, respectively, wherein a driving voltage isapplied to said first, fourth, seventh, and eighth electrodes at apolarity identical to one another and applied to said second, third,sixth, and ninth electrodes at a polarity opposite to said first,fourth, seventh, and eighth electrodes.
 26. The angular rate sensoraccording to claim 25, further comprising: a tenth electrode provided onan inner surface of the other arm of said tuning fork oscillator; andtwo monitor electrodes provided on remaining portions of the first andsecond main surfaces of the other arm, respectively; wherein, when saidfifth electrode is provided on the inner surface of the one of the arms,said fifth and tenth electrodes are connected to a common port fromwhich a detection signal is detected; and wherein, when said fifthelectrode is provided on the outer surface of the one of the arms, adetection signal is detected from a differential signal between saidfifth and tenth electrodes.
 27. An angular rate sensor comprising: atuning fork oscillator having at least two arms and a base, including: afirst oscillator member of a single crystalline piezoelectric materialhaving at least two arms and a base joining the two arms; and a secondoscillator member of the single crystalline piezoelectric materialhaving a shape substantially identical to a shape of said firstoscillator member, said first and second oscillator members being bondeddirectly to each other in a direction of a thickness and in a directionof a crystallographic axis so that opposite polarities of apiezoelectric effect may be developed along a widthwise direction ofsaid first and second oscillator members; first and second electrodesprovided on first and second main surfaces of one of the arms of saidtuning fork oscillator, respectively; third and fourth electrodesprovided on one of outer and inner surfaces of the one of the arms, saidthird and fourth electrodes being provided on a portion close to saidfirst electrode and a portion close to said second electrode,respectively; a fifth electrode provided on one of the inner and outersurfaces of the one of the arms, said fifth electrode being disposed ona surface opposite to the surface on which said third and fourthelectrodes are provided; sixth and seventh electrodes provided on firstand second main surfaces of the other arm of the arms of said tuningfork oscillator, respectively, said sixth and seventh electrodes beingprovided on portions close to an inner surface of the other arm,respectively; and eighth and ninth electrodes provided on the innersurface of the other arm, said eighth and ninth electrodes beingprovided on a portion close to said sixth electrode and a portion closeto said seventh electrode, respectively; wherein a driving voltage isapplied to said first, fourth, seventh, and eighth electrodes at apolarity identical to one another and applied to said second, third,sixth, and ninth electrodes at a polarity opposite to said first,fourth, seventh, and eighth electrodes.
 28. The angular rate sensoraccording to claim 27, further comprising: a tenth electrode provided onan outer surface of said other arm of said tuning fork oscillator; andtwo monitor electrodes provided on remaining portions of the first andsecond main surfaces of the other arm; wherein, when said fifthelectrode is provided on the inner surface of the one of the arms, adetection signal is detected from a differential signal between saidfifth and tenth electrodes; and wherein, when said fifth electrode isprovided on the outer surface of the one of the arms, said fifth andtenth electrodes are connected to a common port from which a detectionsignal is detected.
 29. An angular rate sensor comprising: a tuning forkoscillator having at least two arms and a base, including: a firstoscillator member of a single crystalline piezoelectric material havingat least two arms and a base joining the two arms; and a secondoscillator member of the single crystalline piezoelectric materialhaving a shape substantially identical to a shape of said firstoscillator member, said first and second oscillator members being bondeddirectly to each other in a direction of a thickness and in a directionof a crystallographic axis so that opposite polarities of apiezoelectric effect may be developed along a widthwise direction ofsaid first and second oscillator members; first and second electrodesprovided on first and second main surfaces of one of the arms of saidtuning fork oscillator, respectively; third and fourth electrodesprovided on an outer surface of the one of the arms, said third andfourth electrodes being provided on a portion close to said firstelectrode and a portion close to said second electrode, respectively;fifth and sixth electrodes provided on an inner surface of the one ofthe arms, said fifth and sixth electrodes being provided on a portionclose to said first electrode and a portion close to said secondelectrode, respectively; a seventh electrode provided on one of firstand second main surfaces of other arm of the arms of said tuning forkoscillator; eighth and ninth electrodes provided on an outer surface ofthe other arm, said eighth and ninth electrodes being provided on aportion close to the first main surface of the other arm and a portionclose to the second main surface of the other arm, respectively; andtenth and eleventh electrodes provided on an inner surface of the otherarm, said tenth and eleventh electrodes being provided on a portionclose to the first main surface of the other arm and a portion close tothe second main surface of the other arm, respectively; wherein, whensaid seventh electrode is provided on the first main surface, a drivingvoltage is applied to said first, eighth, and tenth electrodes at apolarity identical to one another and applied to said second, third,fifth, and seventh electrodes at a polarity opposite to said first,eighth, and tenth electrodes; and wherein, when said seventh electrodeis provided on the second main surface, a driving voltage is applied tosaid first and seventh electrodes at a polarity identical to each otherand applied to said second, third, fifth, ninth, and eleventh electrodesat a polarity opposite to said first and seventh electrodes.
 30. Theangular rate sensor according to claim 29, wherein: when said seventhelectrode is provided on the first main surface, said fourth and ninthelectrodes are connected to a common port, said sixth and eleventhelectrodes are connected to another common port, and a detection signalis detected from a differential signal between the common ports; andwhen said seventh electrode is provided on the second main surface, saidfourth and eighth electrodes are connected to a common port, said sixthand tenth electrodes are connected to another common port, and adetection signal is detected from a differential signal between thecommon ports.
 31. The angular rate sensor according to claim 1, whereinthe electrodes provided on the first and second main surfaces of thearms are extended onto a surface of the base.
 32. The angular ratesensor according to claim 1, wherein the electrodes provided on theouter surfaces of the arms are extended onto a surface of the base. 33.The angular rate sensor according to claim 16, further comprising fourmonitor electrodes provided on remaining portions of the first andsecond main surfaces of the arms of said tuning fork oscillator,respectively.
 34. The angular rate sensor according to claim 17, furthercomprising four monitor electrodes provided on remaining portions of thefirst and second main surfaces of the arms of said tuning forkoscillator, respectively.
 35. The angular rate sensor according to claim18, further comprising four monitor electrodes provided on remainingportions of the first and second main surfaces of the arms of saidtuning fork oscillator, respectively.
 36. The angular rate sensoraccording to claim 19, further comprising four monitor electrodesprovided on remaining portions of the first and second main surfaces ofthe arms of said tuning fork oscillator, respectively.
 37. The angularrate sensor according to claim 20, further comprising four monitorelectrodes provided on remaining portions of the first and second mainsurfaces of the arms of said tuning fork oscillator, respectively. 38.The angular rate sensor according to claim 21, further comprising fourmonitor electrodes provided on remaining portions of the first andsecond main surfaces of the arms of said tuning fork oscillator,respectively.
 39. The angular rate sensor according to claim 22, furthercomprising four monitor electrodes provided on remaining portions of thefirst and second main surfaces of the arms of said tuning forkoscillator, respectively.
 40. The angular rate sensor according to claim18, further comprising: two grounding electrodes provided on remainingportions of the first and second main surfaces of the one of the arms ofsaid tuning fork oscillator, respectively; and two monitor electrodesprovided on remaining portions of the first and second main surfaces ofthe other arm.
 41. The angular rate sensor according to claim 20,further comprising: two grounding electrodes provided on remainingportions of the first and second main surfaces of the one of the arms ofsaid tuning fork oscillator, respectively; and two monitor electrodesprovided on remaining portions of the first and second main surfaces ofthe other arm.
 42. The angular rate sensor according to claim 22,further comprising: two grounding electrodes provided on remainingportions of the first and second main surfaces of the one of the arms ofsaid tuning fork oscillator, respectively; and two monitor electrodesprovided on remaining portions of the first and second main surfaces ofthe other arm.
 43. The angular rate sensor according to claim 3, whereinthe electrodes provided on the first and second main surfaces of thearms are extended onto a surface of the base.
 44. The angular ratesensor according to claim 5, wherein the electrodes provided on thefirst and second main surfaces of the arms are extended onto a surfaceof the base.
 45. The angular rate sensor according to claim 7, whereinthe electrodes provided on the first and second main surfaces of thearms are extended onto a surface of the base.
 46. The angular ratesensor according to claim 11, wherein the electrodes provided on thefirst and second main surfaces of the arms are extended onto a surfaceof the base.
 47. The angular rate sensor according to claim 15, whereinthe electrodes provided on the first and second main surfaces of thearms are extended onto a surface of the base.
 48. The angular ratesensor according to claim 17, wherein the electrodes provided on thefirst and second main surfaces of the arms are extended onto a surfaceof the base.
 49. The angular rate sensor according to claim 19, whereinthe electrodes provided on the first and second main surfaces of thearms are extended onto a surface of the base.
 50. The angular ratesensor according to claim 21, wherein the electrodes provided on thefirst and second main surfaces of the arms are extended onto a surfaceof the base.
 51. The angular rate sensor according to claim 25, whereinthe electrodes provided on the first and second main surfaces of thearms are extended onto a surface of the base.
 52. The angular ratesensor according to claim 27, wherein the electrodes provided on thefirst and second main surfaces of the arms are extended onto a surfaceof the base.
 53. The angular rate sensor according to claim 29, whereinthe electrodes provided on the first and second main surfaces of thearms are extended onto a surface of the base.
 54. The angular ratesensor according to claim 3, wherein the electrodes provided on theouter surfaces of the arms are extended onto a surface of the base. 55.The angular rate sensor according to claim 4, wherein the electrodesprovided on the outer surfaces of the arms are extended onto a surfaceof the base.
 56. The angular rate sensor according to claim 5, whereinthe electrodes provided on the outer surfaces of the arms are extendedonto a surface of the base.
 57. The angular rate sensor according toclaim 6, wherein the electrodes provided on the outer surfaces of thearms are extended onto a surface of the base.
 58. The angular ratesensor according to claim 7, wherein the electrodes provided on theouter surfaces of the arms are extended onto a surface of the base. 59.The angular rate sensor according to claim 8, wherein the electrodesprovided on the outer surfaces of the arms are extended onto a surfaceof the base.
 60. The angular rate sensor according to claim 9, whereinthe electrodes provided on the outer surfaces of the arms are extendedonto a surface of the base.
 61. The angular rate sensor according toclaim 11, wherein the electrodes provided on the outer surfaces of thearms are extended onto a surface of the base.
 62. The angular ratesensor according to claim 12, wherein the electrodes provided on theouter surfaces of the arms are extended onto a surface of the base. 63.The angular rate sensor according to claim 13, wherein the electrodesprovided on the outer surfaces of the arms are extended onto a surfaceof the base.
 64. The angular rate sensor according to claim 15, whereinthe electrodes provided on the outer surfaces of the arms are extendedonto a surface of the base.
 65. The angular rate sensor according toclaim 17, wherein the electrodes provided on the outer surfaces of thearms are extended onto a surface of the base.
 66. The angular ratesensor according to claim 19, wherein the electrodes provided on theouter surfaces of the arms are extended onto a surface of the base. 67.The angular rate sensor according to claim 21, wherein the electrodesprovided on the outer surfaces of the arms are extended onto a surfaceof the base.
 68. The angular rate sensor according to claim 25, whereinthe electrodes provided on the outer surfaces of the arms are extendedonto a surface of the base.
 69. The angular rate sensor according toclaim 27, wherein the electrodes provided on the outer surfaces of thearms are extended onto a surface of the base.
 70. The angular ratesensor according to claim 29, wherein the electrodes provided on theouter surfaces of the arms are extended onto a surface of the base.